Abstract

The phenomenon of electrical alternans of the ST segment during periods of ST elevation in Prinzmetal's angina is of great clinical interest. In our experience it appears to be a sign in the surface electrocardiogram (ECG) reflecting an unstable electrical state frequently heralding serious ventricular arrhythmias (1, 2). Occurring in about 30% of all episodes of Prinzmetal's angina (1, 2), but never observed during ST elevation of an evolving myocardial infarction, it appears to be highly specific for Prinzmetal's angina in humans. Its occurrence may thus allow distinction between the two conditions at the bedside. The phenomenon of ST alternans